Scientists have identified the genetic changes which altered our skeleton in our evolution from apes to humans

Evolution of the bones of great apes to human occurring around 2 million years ago was accelerated
Evolution of the bones of great apes to human occurring around 2 million years ago was accelerated. Image: MikeB

This is not about the human-animal relationship which is the prime topic of this website but about the human-animal and our evolution from the great apes.

Scientists at a number of institutions and universities – primarily Texas University and Columbia – have identified the genetic changes which took place during our evolution from apes to humans and which enabled our ancient ancestors to stand upright on two legs about 2 million years ago.

They discovered that there was an accelerated process of evolution with respect to the genes which controlled the bones which enabled humans to stand upright. That’s my understanding.

Humans are the only primates to have longer legs and arms. This was an evolutionary change in the form of the skeleton of apes. It was a critical one which enabled apes to evolve into humans through the ability to walk on two legs.

And the scientists wanted to work out which genetic changes were behind the anatomical differences which are visible in the fossil records and which led to modern humans from Australopithecus to Neanderthals.

They used artificial intelligence to examine more than 30,000 full-body x-rays stored in the UK biobank which is a repository containing genetic data from more than half a million volunteers.

They also measured 23 skeletal features such as shoulder width, torso length and the angle of tibia to fibula. They compared this information with the genomic data stored in the biobank. This enabled them to identify 145 regions of the chromosome which govern skeletal proportions. Most of them were previously unknown.

They found that in many of these regions there was an evolution at an accelerated pace compared with the same genes in great apes.

I understand that to mean that there was an accelerated evolution of our ancient ancestors, the great apes, to the human animal in respect of certain genes and it is those genes which control the length of our bones which in turn lengthened our legs and which in turn allowed us to walk on two legs with arms that are much shorter than our legs.

That’s the way I interpret it in a nutshell.

Dr. Vagheesh Narasimhan, a biology and statistics professor at the University of Texas who I believe is a co-author of the study, said:

What we are seeing is the first genomic evidence that there was selective pressure on genetic variants that affect skeletal proportions, enabling a transition from knuckle-based walking to bipedalism.

Dr. Vagheesh Narasimhan

He saying that evolution put pressure on the genes affecting the length of the leg of apes to evolve to create longer legs. And for me that’s the way evolution works. The objective of evolution is to improve survivability. Clearly, it was found by chance that apes with longer legs who were more able to walk on two legs rather than dragging the knuckles of their hands around, were better able to survive. And this put selective pressure upon the genes controlling the skeletal proportions.

The study has been published in the journal Science. They noted that “the genetic basis of skeletal proportions” had not been well documented. The researchers wanted to identify the genes which govern our skeletons so that they can explain how humans developed a “distinctive skeletal form”. It’s a form which set us apart from other primates.

They added that “Whether natural selection has acted on these genes to alter the development of limb proportions, thus allowing us to walk upright, [had] remained unknown.”

They believe that the changes in the anatomical portions of the human skeleton from the skeleton of apes occurred around the separation of the human and chimpanzee lineages.

The study also looked at the way these changes affected the prevalence of arthritis. For example, the study showed that “individuals with a higher ratio of hip width to height were found to be more likely to develop osteoarthritis pain in their hips”. The quote comes from The University of Texas at Austin. The other quotes come from the study itself.

My thank to The Times newspaper and their article by Kaya Burgess of July 21, 2023 and the article on The University of Texas at Austin website.

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